Genetic profiles of subcutaneous panniculitis-like T-cell lymphoma and clinicopathological impact of HAVCR2 mutations

Abstract

Recent studies identified germline mutations in HAVCR2 (encoding T-cell immunoglobulin mucin 3) as a genetic factor that predisposes to subcutaneous panniculitis-like T-cell lymphoma (SPTCL). However, the differences between HAVCR2-mutated (HAVCR2MUT) and HAVCR2 wild-type (HAVCR2WT) SPTCLs remain unclear. A nationwide cohort of 53 patients with SPTCL diagnosed at 8 Korean institutions was established. Whole-exome sequencing and RNA-sequencing were performed on 8 patients in the discovery set. In the validation set, targeted gene sequencing or direct sequencing of HAVCR2 was performed. Of 49 patients with available HAVCR2 status, 25 (51.0%) were HAVCR2Y82C. HAVCR2Y82C was associated with younger age (P = .001), development of hemophagocytic lymphohistiocytosis or hemophagocytic lymphohistiocytosis-like systemic illness (P < .001), and short relapse-free survival (RFS) (P = .023). Most mutated genes in SPTCLs were involved in immune responses, epigenetic modifications, and cell signaling. Mutations in UNC13D, PIAS3, and KMT2D were more frequent in HAVCR2WT SPTCLs. At the gene expression level, HAVCR2Y82C SPTCLs were enriched in genes involved in IL6-JAK-STAT3 signaling and in tumor necrosis factor-α signaling via NF-κB. CCR4 was significantly upregulated in HAVCR2WT SPTCLs both at the messenger RNA level and at the protein level. We established a risk stratification system for SPTCL by integrating clinical and histopathological features, including age and HAVCR2 mutation status. This risk stratification system was strongly associated with RFS (P = .031). In conclusion, the HAVCR2Y82C mutation was common in Korean patients with SPTCL and was associated with unique clinicopathological and genetic features. Combining clinicopathological parameters could aid in predicting prognosis for patients with SPTCL.

Graphical abstract

Figure 1.

Histopathological features of SPTCLs and detection of HAVCR2^Y82C mutations. (A) Excisional biopsy specimen of a 16-year-old female patient with an SPTCL (SP04) exhibited adipocytic rimming by CD8-positive lymphocytes along with prominent necrosis. This patient was confirmed by using WES to have a germline homozygous HAVCR2^Y82C mutation. (B) Lipogranulomatous inflammation was observed in a 54-year-old female patient (SP44), and TGS revealed heterozygous HAVCR2^Y82C mutations. SP14 harbored heterozygous HAVCR2^Y82C mutations, which could be inferred from double peaks on the electropherogram. (C) A 45-year-old female patient (SP52) with the HAVCR2^WT genotype had both necrosis and granuloma formation. (D) Lipogranulomatous inflammation was observed in the HAVCR2^WT SPTCL of a 53-year-old woman (SP39).

Figure 2.

Mutational landscape of SPTCLs and other cutaneous T-cell lymphomas with panniculitic presentation in Korean patients. Integrated mutation map of Korean SPTCLs and previously reported data sets. A subset of genetic alterations was shared with PCGDTCL and MFs; however, the HAVCR2^Y82C mutation was seen exclusively in SPTCLs. Genes that were more frequently mutated in HAVCR2^WT SPTCLs are indicated with asterisks; statistical significance was determined by using Fisher’s exact test. ATP, adenosine triphosphate.

Figure 3.

GSEA and DEGs between HAVCR2^Y82C and HAVCR2^WT SPTCLs. (A) Significantly enriched gene sets in HAVCR2^Y82C SPTCLs and their NES are shown. (B) Most enriched gene set in HAVCR2^Y82C SPTCLs were associated with increased inflammatory responses. (C) Higher number of pSTAT3-positive cells characterizes HAVCR2^Y82C SPTCLs. (D) Volcano plot highlighting 52 genes differentially expressed according to HAVCR2 genotype. (E) CCR4 and Foxp3 positivity was assessed by using IHC. Correlation plot showing percentages of CCR4- and Foxp3-positive cells; circled cross indicates outlier results. (F and G) HAVCR2^WT SPTCLs had a significantly higher number of CCR4-positive cells and Foxp3-positive cells compared with HAVCR^Y82C SPTCLs (Mann-Whitney U test).

Figure 4.

Double-staining for Foxp3 and CCR4. Double-staining showed the cells coexpressing Foxp3 and CCR4 (arrow) as well as the cells only positive for CCR4 (arrowhead), suggesting the presence of non-Treg CCR4-positive cells within the tumor microenvironment of SPTCL.

Figure 5.

Survival analyses according to clinicopathological factors and development of an SPTCL risk stratification score. (A and B) The presence of the HAVCR2^Y82C mutation and age <30 years at diagnosis, respectively, were significant prognostic factors in patients with SPTCLs. (C) A tendency toward poor outcomes was observed in patients with tissue necrosis. (D-F) HLH (or HLH-like systemic illness), pSTAT3 positivity, and lower CCR4 expression were not significantly associated with RFS. (G) The risk score system integrating patients’ age and HAVCR2 status was significantly associated with RFS (P = .031). Patients with score 2 had a shorter RFS compared with patients with score 0 (log-rank test, P = .024). However, there were no significant differences between scores 2 vs 1 and scores 1 vs 2 (log-rank test, P = .068 and 0.354, respectively). (H) Significant correlation between the risk score and event of systemic complication was observed in the current study population (P = .005, linear-by-linear test) as well as in the pooled analysis using the published data from Gayden et al and Polprasert et al (P < .001, linear-by-linear test).